JP5000314B2 - Molding condition determination system and molding condition determination method for press machine - Google Patents

Description

  The present invention relates to a molding condition determination system and a molding condition determination method for press molding. For example, the present invention relates to a molding condition determination system and a molding condition determination method for press molding for manufacturing an automobile body.

Conventionally, when forming a body of an automobile by drawing a steel plate, an optimum forming condition is determined by actually repeating trial production of a formed product using a press machine.
Incidentally, in recent years, a servo press using a servo motor is known. In this servo press machine, since the slide speed and the die cushion pressure can be freely changed during molding, the degree of freedom of press molding is high and the cycle time can be shortened.

For example, the following methods have been proposed as a method for controlling the slide speed. In other words, the relationship between the material pull-in amount and the punch stroke is analyzed and stored in the database as an ideal machining curve. During actual machining, the relationship between the workpiece pull-in amount and the punch stroke is acquired and stored. Based on the processing curve, the punch speed is feedback controlled (see Patent Document 1).
According to this method, the productivity of the molded product can be improved by controlling the punching speed in real time.
Japanese Patent No. 3768410

  However, in the servo press described above, it is necessary to make a large number of trials in order to determine the speed and the die cushion pressure. As a result, there is a problem that man-hours increase and costs increase. Even if the method disclosed in Patent Document 1 is adopted, the same problem arises in order to create an ideal machining curve.

  An object of the present invention is to provide a molding condition determination system and a molding condition determination method for a press that can reduce costs.

  The molding condition determination system for a press machine according to the present invention is a molding condition determination system for determining a molding condition for a press machine, and is a die cushion pressure optimizing means for optimizing a die cushion pressure, and a slide for optimizing a slide speed. A speed optimizing unit and a molding condition determining unit that determines whether or not the quality of the press-molded product reaches a certain standard based on the result of the molding simulation analysis. Until it is determined that the quality reaches a certain standard, the die cushion pressure optimizing means, the molding condition determining means, the slide speed optimizing means, and the molding condition determining means are repeated in this order.

According to the present invention, since the die cushion pressure and the slide speed can be automatically determined, the number of trial productions using actual press machines and materials can be greatly reduced, and the cost can be reduced. Furthermore, a product having a complicated shape can be molded by predicting molding conditions at the stage of designing the product shape.
In particular, in the servo press machine, since the slide speed and die cushion pressure can be freely changed during molding, the number of trial productions can be greatly reduced.

  In this case, the molding condition determination means determines that the quality of the press-formed product is constant based on the minimum principal strain and the sheet thickness reduction rate, or the minimum principal strain and the equivalent plastic strain, which are output as a result of the molding simulation analysis. It is preferable to determine whether or not

It has been found that when the plate thickness reduction rate and the equivalent plastic strain are increased, cracks are likely to occur, and when the minimum principal strain is decreased, wrinkles and surface strain are easily generated.
Therefore, according to the present invention, the molding condition determination means determines whether the quality of the press-formed product reaches a certain standard based on the minimum principal strain and the sheet thickness reduction rate, or the minimum principal strain and the equivalent plastic strain. Since it determined, the malfunction of a press molded product can be predicted reliably.

  In this case, it is preferable that a molding simulation unit that executes a molding simulation using a stress-strain relationship is provided, and the molding simulation unit determines the stress-strain relationship in consideration of a strain rate.

  In this case, it is preferable that the molding simulation means execute a molding simulation using a friction coefficient, and determine the friction coefficient in consideration of a sliding speed and a contact surface pressure between the material and a die of the press machine. .

In the conventional molding simulation, the coefficient of friction was determined corresponding to the mold shape, but the sliding speed between the material and the mold and the contact surface pressure were not taken into account, and the stress-strain relationship was also considered. The strain rate was not taken into account. Therefore, it has been difficult to perform a molding simulation with high accuracy on a servo press machine in which the slide speed and die cushion pressure change during molding.
According to the present invention, the friction coefficient is determined in consideration of the sliding speed and the contact surface pressure between the material and the die of the press machine. Moreover, the stress-strain relationship was determined in consideration of the strain rate. Therefore, it is possible to execute the molding simulation for the servo press machine in which the slide speed and the die cushion pressure change with high accuracy.

  The molding condition determination method for a press machine according to the present invention is a molding condition determination method for determining a molding condition for a press machine, which is a die cushion pressure optimization procedure for optimizing the die cushion pressure, and a slide for optimizing the slide speed. A speed optimization procedure, a molding simulation analysis, and a molding condition determination procedure for determining whether or not the quality of the press-molded product reaches a certain standard based on the analysis result. The die cushion pressure optimization procedure, the molding condition determination procedure, the slide speed optimization procedure, and the molding condition determination procedure are repeated in this order until it is determined that the quality of the press-formed product reaches a certain standard.

  In this case, in the molding condition determination procedure, the quality of the press-formed product is set to a certain standard based on the minimum principal strain and the sheet thickness reduction rate, or the minimum principal strain and the equivalent plastic strain, which are output as the molding simulation analysis result. It is preferable to determine whether or not it is reached.

  In this case, in the molding condition determination procedure, it is preferable that a molding simulation is executed using a stress-strain relationship, and the stress-strain relationship is determined in consideration of a strain rate.

  In this case, in the molding condition determination procedure, a molding simulation is executed using a friction coefficient, and the friction coefficient is determined in consideration of the sliding speed and contact surface pressure between the material and the die of the press machine. preferable.

  The above-described molding condition determination method for a press machine is an expansion of the above-described molding condition determination system as a molding condition determination method for a press machine, and has the same effect as the above-described molding condition determination system.

  According to the present invention, since the die cushion pressure and the slide speed can be automatically determined, the number of trial productions using actual press machines and materials can be greatly reduced, and the cost can be reduced. Furthermore, a product having a complicated shape can be molded by predicting molding conditions at the stage of designing the product shape. In particular, in the servo press machine, since the slide speed and die cushion pressure can be freely changed during molding, the number of trial productions can be greatly reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a molding condition determination system 1 according to an embodiment of the present invention. The molding condition determination system 1 includes an arithmetic processing device 10 that is connected to a press machine 30 and executes various programs, and a storage device 20 that stores information such as a hard disk.
The press machine 30 is a servo press machine driven by a servo, and the molding condition determination system 1 outputs press molding conditions including a slide speed and a die cushion pressure to the press machine 30.

  The molding condition determination system 1 includes a molding condition optimization unit 11, a molding simulation unit 12, and a press control data generation unit 13 as programs developed on an OS (Operating System) that performs operation control.

The molding simulation means 12 performs simulation analysis of the molding process. When an analysis condition is input, the molding simulation unit 12 performs a molding simulation under the analysis condition and outputs the analysis result.
The storage device 20 is a database and stores operating conditions of the press machine 30 such as a slide speed range, a slide acceleration range, and a die cushion pressure range. These operating conditions are set in advance based on the cycle time, the conveyance speed, and the like.

The molding condition optimizing unit 11 generates a plurality of types of molding conditions with reference to the operation conditions stored in the storage device 20, and outputs these molding conditions to the molding simulation unit 12 as analysis conditions. Thereafter, an analysis result is received from the molding simulation means 12, and optimum molding conditions are determined based on the analysis result.
The press control data generation unit 13 generates data for operating the press machine 30 based on the molding conditions determined by the molding condition optimization unit 11.

FIG. 2 is a diagram illustrating a schematic configuration of the press machine 30.
The press machine 30 is a so-called servo press machine, and causes the upper mold 51 to approach and separate from the lower mold mechanism 40 having the lower mold 41 disposed on the lower side of the steel plate 32 as a workpiece and the lower mold 41. An upper mold mechanism 50 and a control device 31 that controls the lower mold mechanism 40 and the upper mold mechanism 50 are provided.

  The upper mold mechanism 50 includes a servo motor 52, a reduction gear 53 that is rotationally driven by the servo motor 52, a rotary plate 54 that is rotationally driven by the reduction gear 53 with a large torque, and an upper end on the side surface of the rotary plate 54. The part has a connecting rod 55 pivotally supported.

  The servo motor 52 is, for example, an AC type, and has high responsiveness and small torque unevenness. The shaft rotation position of the servo motor 52 is detected by an encoder (not shown), and the servo motor 52 is feedback-controlled based on the detected shaft rotation position.

  The upper mold mechanism 50 further includes a slider 56 that is pivotally supported at the lower end of the connecting rod 55, and the upper mold 51 is provided on the lower surface of the slider 56.

  The upper die 51 is pressed by pressing the steel plate 32 together with the lower die 41, and a die surface 51a for contacting the upper surface of the steel plate 32 is provided on the lower surface. This 51 is a concave curved surface, and an annular holder 57 is provided around the upper mold 51. The front end surface of the holder 57 is horizontal and slightly protrudes from the mold surface 51a. Therefore, the holder 57 comes into contact with the steel plate 32 prior to the mold surface 51a.

  In addition to the lower mold 41, the lower mold mechanism 40 includes a fixed base 42 that serves as a base, an annular blank holder 43 that supports the periphery of the steel plate 32, and a die cushion mechanism 44 that raises and lowers the blank holder 43. .

  The lower die 41 is provided on the upper part of the fixed base 42 and presses the steel plate 32 together with the upper die 51. On the upper surface of the lower mold 41, a mold surface 41a for contacting the lower surface of the steel plate 32 is provided.

  The blank holder 43 is provided at a position facing the holder 57, and sandwiches the end portion of the steel plate 32 together with the holder 57 in order to prevent wrinkles and displacement when the steel plate 31 is pressed.

  The die cushion mechanism 44 includes a plurality of pins 45 that pass through the fixed base 42 and the lower mold 41 from below and support the lower portion of the blank holder 54, and a hydraulic lifting mechanism (not shown) that lifts and lowers these pins 45. .

  The lifting mechanism includes a hydraulic cylinder (not shown) connected to the pin 45 and a servo device (not shown) that drives the hydraulic cylinder. This servo device is connected to the control device 31 and performs a predetermined pressure control based on a signal from the control device 31, so that the peripheral portion of the steel plate 32 is appropriately pressured by the blank holder 43 and the holder 57. Press (die cushion pressure) to suppress wrinkles.

  The control device 31 drives the servo motor 52 to move the upper die 51 forward and backward relative to the lower die 41 and drives the die cushion mechanism 44 to raise and lower the blank holder 43.

  A procedure for processing the steel plate 32 using the press machine 30 will be described with reference to FIG.

  First, in step S1, initial setting is performed. That is, the blank holder 43 is raised to a predetermined position, and the blank steel plate 32 is supported by the blank holder 43. Further, the upper mold 51 is raised to the top dead center. Next, in step S <b> 2, under the action of the control device 31, the servo motor 52 is rotationally driven to lower the slider 56.

  When the slider 56 is lowered to some extent, the holder 57 comes into contact with the upper surface of the steel plate 32, and the steel plate 32 is held between the holder 57 and the blank holder 43. From this point, the blank holder 57 is lowered under the action of the control device 31 (step S3). Specifically, under the action of the control device 31, the blank holder 57 generates an appropriate force so that the lower surface of the steel plate 32 appears to be pressed, and pressure control is performed so that the blank holder 57 is lowered while securely holding the steel plate 32. . That is, the blank holder 57 is pressed through the steel plate 32 by the holder 57 and is pressed down while applying an appropriate pressure to the steel plate 32. Thereby, the steel plate 32 is lowered while the peripheral portion is held (clamped) by the holder 57 and the blank holder 43, and is gradually pressed into the product shape by the upper die 51 and the lower die 41.

  In step S4, the control device 31 causes the position of the slider 56 to reach the bottom dead center (that is, the lowest point during one stroke of the upper mold 51). In step S5, under the action of the control device 31, the servo motor 52 is rotationally driven to raise the slider 56 to the panel transport position.

  In step S6, it is confirmed whether or not the position of the slider 56 has reached the panel transport position. If it has reached, the process proceeds to step S7, and if not reached, the slider 56 continues to rise. In step S <b> 7, the blank holder 43 is raised under the action of the control device 31. As a result, the blank holder 43 rises slightly later than the slider 56.

  In step S8, the blank holder 43 is raised to the panel transport position under the action of the control device 31. In step S9, the raising of the blank holder 43 is temporarily stopped, and the steel plate 32 that has been subjected to the draw forming process is transported to the next process station by a transport means (not shown).

  In step S10, the control device 31 raises the blank holder 43 again to reach the blank holder 43 to the processing standby position. In step S11, an unprocessed steel plate is placed at a predetermined position. During this time, the slider 56 continues to rise. In step S12, the control device 31 causes the slider 56 to reach the top dead center.

Next, the displacement of the slider of the press machine 30 will be described with reference to FIG.
In the above-described draw molding, the drawing is performed by displacing the slider 56, that is, the upper die 51 as shown in FIG. Specifically, the upper mold 51 is lowered from the top dead center (X1) at a predetermined slide speed, and the speed is decreased just before the position (X2) in contact with the steel sheet. Then, press molding is performed while increasing the speed. When the upper mold 51 reaches the bottom dead center (X0), the upper mold 51 is raised at the original slide speed (predetermined speed).

FIG. 5 is a block diagram showing a schematic configuration of the molding condition optimizing means 11.
The molding condition optimization unit 11 includes a molding condition generation unit 60, a die cushion pressure optimization unit 61, a slide speed optimization unit 62, and a molding condition determination unit 63.
The molding condition generation means 60 refers to the operating conditions stored in the storage device 20 and generates a plurality of types of molding conditions with different combinations of slide speed and die cushion pressure.

The die cushion pressure optimizing unit 61 selects an optimum die cushion pressure from among the molding conditions generated by the molding condition generating unit 60.
The slide speed optimizing means 62 selects the molding condition generated by the molding condition generating means 60 and having the optimum slide speed.
Based on the result of the molding simulation analysis performed by the molding simulation unit 12, the molding condition determination unit 63 determines whether the quality of the press-formed product reaches a certain standard.

  The molding condition optimizing unit 11 operates the molding condition generating unit 60, and thereafter the die cushion pressure optimizing unit 61 until the molding condition determining unit 63 determines that the quality of the press-molded product reaches a certain standard, The molding condition determination unit 63, the slide speed optimization unit 62, and the molding condition determination unit 63 are repeated in this order.

Next, the operation of the molding condition optimizing means 11 will be described using the flowchart of FIG.
First, in S11, a plurality of molding conditions with different combinations of slide speed and die cushion pressure are generated by the molding condition generating means 60, and the generated combinations are output to the molding simulation means 12 as analysis conditions. Receive analysis results from.

In S12, the die cushion pressure optimizing means 61 optimizes the die cushion pressure of the press machine.
FIG. 7 is a diagram showing the relationship between the die cushion pressure of the press machine and the molding time.
As shown in FIG. 7, the die cushion pressure is set in two stages, the first half and the second half of the molding time. Therefore, optimum values are searched for the die cushion pressure in the first half of the molding time, the die cushion pressure in the second half of the molding time, and the switching timing of the die cushion pressure.

In S13, the molding condition determination unit 63 determines whether the quality of the press-molded product reaches a certain standard based on the molding simulation analysis result. Specifically, using the maximum value and the minimum principal strain of the sheet thickness reduction rate as an index for evaluating a molded product, the maximum value of the sheet thickness reduction rate is not more than a predetermined value, and the minimum principal strain is a predetermined value. It is determined whether it is above.
This is because cracks (breaks) are likely to occur when the plate thickness reduction rate is increased, and wrinkles and surface strains are likely to occur when the minimum principal strain is reduced.

  When the determination in S13 is No, the die cushion pressure optimized in S12 is selected so that the maximum value of the plate thickness reduction rate is equal to or less than a predetermined value, and the process proceeds to S14. On the other hand, if the determination in S13 is Yes, the process ends.

In S14, the slide speed optimizing means 62 optimizes the slide speed of the press.
FIG. 8 is a diagram showing the relationship between the slide speed of the press machine and the molding time.
As shown in FIG. 8, the optimum value is searched for the maximum value of the slide speed and the period during which the slide speed is maximum.

In S15, as in S13, based on the forming simulation analysis result, it is determined whether the quality of the press-formed product reaches a certain standard using the maximum value and the minimum principal strain of the sheet thickness reduction rate.
If the determination in S15 is No, the process moves to S16, and if the determination is Yes, the process ends.

  In S16, the die cushion pressure is optimized again. This is because the die cushion pressure is optimized in S12, but the slide speed is optimized in S14, so that the die cushion pressure needs to be finely adjusted.

In S17, as in S13, based on the forming simulation analysis result, it is determined whether the quality of the press-formed product reaches a certain standard using the maximum value of the plate thickness reduction rate and the minimum principal strain.
If the determination in S17 is No, the process returns to S14, and if the determination is Yes, the process ends.

Next, the operation of the molding simulation means 12 will be described using the flowchart of FIG.
In S31, molding conditions are input. Specifically, the die shape of the press machine 30, the shape of the workpiece, the slide speed, the die cushion pressure, the stress-strain relationship of the workpiece, and the friction coefficient are input. Here, the stress-strain characteristics depend on the strain rate, and the friction coefficient depends on the sliding speed between the workpiece and the mold and the contact surface pressure.

  In S32, it is determined whether or not deformation occurs. If this determination is Yes, the process moves to S33, and if No, the process moves to S36.

  In S33, the strain rate of the deformed portion is calculated, and in S34, the stress-strain relationship is determined based on this strain rate. The determination of the stress-strain relationship is performed every predetermined cycle until the end time is reached.

FIG. 10 is a diagram showing a stress-strain relationship.
As shown in FIG. 10, the stress-strain relationship depends on the strain rate, and the stress at the same strain amount tends to increase as the strain rate increases.
Specifically, the strain rates at the same strain amount decrease in the order of strain rates 10, 1, 0.1, and 0.01.

Further, as shown in FIG. 11, when the strain rate changes during the deformation, the stress-strain relationship after the strain rate changes depends only on the strain rate after the change, regardless of the strain rate before the change. It has been found. That is, the stress-strain relationship after the strain rate changes is not affected by the speed history before the strain rate changes.
Specifically, even if the strain rate is 1, 0.1, or 0.01, when the strain rate changes to 0.1, the stress follows the graph of the strain rate of 0.1.

Therefore, the stress-strain relationship is defined as follows using equivalent stress and equivalent plastic strain. The equivalent stress is a stress converted to uniaxial tension, and the equivalent plastic strain is a plastic strain converted to uniaxial tension. By converting in this way, the comparison can be made easily and the strength evaluation becomes easy.
That is, as shown in FIG. 12, the relationship between a predetermined equivalent plastic strain and an equivalent stress is determined for a predetermined strain rate by experiments or the like, and point sequence data is generated.

  Here, the predetermined strain rate is 0.01, 0.1, 1, 10, and the predetermined equivalent plastic strain is 0, 0.05, 0.1, 0.15, 0.2, 0.25. As shown in FIG. These point sequence data were plotted on a graph as shown in FIG. 13, and the points were connected with a straight line.

Note that if the strain rate and equivalent plastic strain to be calculated are not included in the above point sequence data, the equivalent stress-equivalent plastic strain relationship cannot be obtained directly from the point sequence data. Ask in the procedure.
When the equivalent plastic strain value to be calculated is located between the two equivalent plastic strains defined in FIG. 13, the equivalent stress-equivalent plastic strain relationship is obtained using the interpolation value of these two equivalent plastic strains. Ask for.

When the strain rate to be calculated is located between the two strain rates defined in FIG. 13, the equivalent stress-equivalent plastic strain relationship is obtained using the interpolation value of these two strain rates.
In addition, the above interpolation value may be calculated | required using a linear function (straight line), and may be calculated | required using a quadratic or more function.

  However, when the strain rate to be calculated is larger than the maximum strain rate defined in FIG. 13, the equivalent stress-equivalent plastic strain relationship at the defined maximum strain rate is used. When the strain rate to be calculated is smaller than the minimum strain rate defined in FIG. 13, the equivalent stress-equivalent plastic strain relationship at the defined minimum strain rate is used. That is, an extrapolated value of strain rate is not used.

For example, as shown in FIG. 14, the point sequence data of the strain rate x is xa, xb, xc, and the point sequence data of the strain rate y is ya, yb, yc.
When obtaining the equivalent stress at the equivalent plastic strains d and e at the strain rate z, first, the interpolated values of the point sequence data of the two strain rates x and y are set as the point sequence data of the strain rate z. Of the point sequence data of the strain rate z, the interpolated values of the equivalent stresses za, zb, and zc at the equivalent plastic strains a, b, and c are set as equivalent stresses at the equivalent plastic strains d and e at the strain rate z. .
Thereby, as shown by the thick line A in FIG. 14, the equivalent stress-equivalent plastic strain relationship at an arbitrary strain rate can be easily calculated, and even if the strain rate changes during the deformation, the strain rate changes. The equivalent stress-equivalent plastic strain relationship can be easily calculated.

  In S35, the stress of the deformed portion is calculated using the selected equivalent stress-equivalent plastic strain relationship. In S36, it is determined whether or not the workpiece and the mold are in contact with each other. If this determination is Yes, the process moves to S37, and if No, the process moves to S41.

In S37, the sliding speed between the workpiece and the mold is calculated, and in S38, the contact surface pressure between the workpiece and the mold is calculated.
Subsequently, in S39, the friction coefficient is determined based on the sliding speed and the contact surface pressure between the workpiece and the mold. The determination of the friction coefficient is performed every predetermined cycle until the end time is reached.

FIG. 15 is a diagram illustrating the relationship between the sliding speed, the contact surface pressure, and the friction coefficient.
As shown in FIG. 15, when there is a fluid having a lubricating function such as cleaning oil between the workpiece and the mold, the friction coefficient depends on the sliding speed between the workpiece and the mold, and the sliding speed is The larger the size, the smaller the tendency.
In addition, as the contact surface pressure between the workpiece and the tool increases, the friction coefficient tends to greatly depend on the sliding speed. That is, as the contact surface pressure between the workpiece and the tool increases, the friction coefficient decreases as the sliding speed increases.
In the draw forming, the contact area between the workpiece and the mold is small, so the contact surface pressure increases. In the overhang forming, the contact area is large, so the contact surface pressure tends to decrease.

Therefore, the relationship between the sliding speed and contact surface pressure and the friction coefficient is defined as follows.
That is, as shown in FIG. 16, the relationship between a predetermined sliding speed and a friction coefficient is obtained for a predetermined contact surface pressure by experiment or the like, and is set as point sequence data.
Here, the predetermined contact surface pressure was 1, 2, 5, 10, and the predetermined sliding speed was 1, 5, 10, 50, 100, 200. These point sequence data were plotted on a graph as shown in FIG. 17, and the points were connected with a straight line.

If the sliding speed and contact surface pressure to be calculated are not included in the above point sequence data, the relationship between the sliding speed and contact surface pressure and the friction coefficient is obtained directly from the point sequence data. Since it is not possible, it asks in the following procedures.
When the sliding speed to be calculated is located between the two sliding speeds defined in FIG. 16, the sliding speed and the contact surface pressure are calculated using the interpolation values of these two sliding speeds. Find the relationship with the coefficient of friction.

When the contact surface pressure to be calculated is located between the two contact surface pressures defined in FIG. 16, the sliding speed and the contact surface pressure are calculated using the interpolated values of these two contact surface pressures. Find the relationship with the coefficient of friction.
In addition, the above interpolation value may be calculated | required using a linear function (straight line), and may be calculated | required using a quadratic or more function.

  However, when the contact surface pressure to be calculated is larger than the maximum contact surface pressure defined in FIG. 16, the relationship between the sliding speed and the contact surface pressure at the defined maximum contact surface pressure and the friction coefficient. Is used. When the contact surface pressure to be calculated is smaller than the minimum contact surface pressure defined in FIG. 16, the relationship between the sliding speed at the defined minimum contact surface pressure, the contact surface pressure, and the friction coefficient. Is used. That is, the extrapolated value of the contact surface pressure is not used.

For example, as shown in FIG. 17, point sequence data with a contact surface pressure of 5 kgf / cm 2 is pf and pg, and point sequence data with a contact surface pressure of 10 kgf / cm 2 is qf and qg.
When obtaining the friction coefficient at the sliding speed h of the contact surface pressure of 8 kgf / cm2, first, the interpolated value of the point sequence data of the two contact surface pressures of 5 kgf / cm2 and the contact surface pressure of 10 kgf / cm2 is obtained as the contact surface pressure of 8 kgf / cm2. It is point sequence data of cm2. Of the point sequence data of the contact surface pressure of 8 kgf / cm 2, the interpolated values of the friction coefficients rf and rg at the sliding speeds f and g are used as the friction coefficient at the sliding speed h of the contact surface pressure of 8 kgf / cm 2. .

Subsequently, in S40, the contact reaction force of the contacting portion is calculated, and in S41, the equation of motion of each element is solved. In S42, it is determined whether or not the end time has been reached. If this determination is No, the process returns to S32, and if Yes, the result is output (S43) and the process ends.
This output result includes the plate thickness reduction rate as an indicator of cracks and the minimum principal strain as an indicator of wrinkles and surface strain.

According to this embodiment, there are the following effects.
(1) Since the molding condition optimization unit 11, the molding simulation unit 12, and the press control data generation unit 13 are provided in the molding condition determination system 1, the die cushion pressure and the slide speed can be automatically determined. The number of prototypes using presses and materials can be greatly reduced, and costs can be reduced. Furthermore, a product having a complicated shape can be molded by predicting molding conditions at the stage of designing the product shape.
In particular, in the servo press machine 30, since the slide speed and the die cushion pressure can be freely changed during molding, the number of trial productions can be greatly reduced.

  (2) Since the molding condition determination means 63 determines whether or not the quality of the press-formed product reaches a certain standard based on the plate thickness reduction rate and the minimum principal strain, it is possible to reliably predict the malfunction of the press-formed product. .

  (3) The friction coefficient was determined in consideration of the sliding speed and contact surface pressure between the material and the die of the press machine, and the stress-strain relationship was determined in consideration of the strain rate. Therefore, a molding simulation for the servo press machine 30 in which the slide speed and the die cushion pressure change can be executed with high accuracy.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in this embodiment, it is determined whether or not the quality of the press-formed product reaches a certain standard by using the maximum value and the minimum principal strain of the sheet thickness reduction rate. However, the present invention is not limited to this. The main strain may be used to determine whether the quality of the press-formed product reaches a certain standard. This is because cracks (breaks) tend to occur when the equivalent plastic strain increases. Therefore, specifically, it is determined whether or not the maximum value of the equivalent plastic strain is equal to or smaller than a predetermined value and the minimum principal strain is equal to or larger than the predetermined value. When this determination is Yes, it is determined that the quality of the press-formed product reaches a certain standard, and when it is No, it is determined that the quality of the press-formed product does not reach a certain standard.

It is a figure which shows schematic structure of the molding condition determination system which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the press of the molding condition determination system which concerns on the said embodiment. It is a flowchart which shows the process sequence of the press machine which concerns on the said embodiment. It is a figure which shows the relationship between the displacement of the slider of the press which concerns on the said embodiment, and shaping | molding time. It is a block diagram which shows schematic structure of the molding condition optimization means of the molding condition determination system which concerns on the said embodiment. It is a flowchart which shows operation | movement of the molding condition optimization means which concerns on the said embodiment. It is a figure which shows the relationship between the die cushion pressure of the press which concerns on the said embodiment, and molding time. It is a figure which shows the relationship between the slide speed of the press which concerns on the said embodiment, and molding time. It is a flowchart which shows operation | movement of the shaping | molding simulation means of the shaping | molding condition determination system which concerns on the said embodiment. It is a figure which shows the stress-strain relationship in the shaping | molding simulation which concerns on the said embodiment. It is a figure for demonstrating the case where the strain rate in the stress-strain relationship which concerns on the said embodiment changes. It is a figure which shows the point sequence data of the equivalent stress which concerns on the said embodiment. It is the figure which plotted the point sequence data of the equivalent stress which concerns on the said embodiment. It is a figure for demonstrating the procedure which calculates | requires the interpolation value of the equivalent stress which concerns on the said embodiment. It is a figure which shows the relationship between the sliding speed and contact surface pressure, and a friction coefficient in the shaping | molding simulation which concerns on the said embodiment. It is a figure which shows the point sequence data of the friction coefficient which concerns on the said embodiment. It is the figure which plotted the point sequence data of the friction coefficient which concerns on the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding condition determination system 11 Molding condition optimization means 12 Molding simulation means 30 Press machine 60 Molding condition generation means 61 Die cushion pressure optimization means 62 Slide speed optimization means 63 Molding condition determination means

Claims (8)

A molding condition determination system for determining molding conditions of a press machine,
With reference to the stored operating conditions of the press machine, molding condition generating means for generating a plurality of molding conditions with different combinations of die cushion pressure and slide speed;
A die cushion pressure optimizing means for selecting an optimum die cushion pressure among the molding conditions generated by the molding condition generating means ;
Of the molding conditions generated by the molding condition generating means, a slide speed optimizing means for selecting the optimum slide speed;
Molding simulation means for executing molding simulation using the stress-strain relationship, with the molding conditions generated by the molding condition generation means as analysis conditions,
Based on the result of the molding simulation analysis by the molding simulation means, the molding condition determination means for determining whether the quality of the press-molded product reaches a certain standard,
Until the molding condition determining means determines that the quality of the press molded product reaches a certain standard, the die cushion pressure optimizing means, the molding condition determining means, the slide speed optimizing means, and the molding condition determining means are repeated in this order. The molding condition determination system for press machines. In the molding condition determination system for a press according to claim 1,
Whether the quality of the press-formed product reaches a certain standard based on the minimum principal strain and sheet thickness reduction rate, or the minimum principal strain and equivalent plastic strain, which is output as a result of the molding simulation analysis. A molding condition determination system for a press, characterized by determining whether or not. In the molding condition determination system for a press according to claim 1 or 2,
The molding condition determination system for a press machine, wherein the molding simulation means determines the stress-strain relationship in consideration of a strain rate. In the molding condition determination system for a press according to claim 3,
The molding simulation means executes a molding simulation using a friction coefficient,
A molding condition determination system for a press machine, wherein the friction coefficient is determined in consideration of a sliding speed and a contact surface pressure between a material and a mold of the press machine. A molding condition determination method for determining molding conditions of a press machine,
Of the molding conditions generated by the molding condition generating means for generating a plurality of molding conditions having different combinations of die cushion pressure and slide speed with reference to the stored operating conditions of the press machine, the die cushion pressure is optimal. Die cushion pressure optimization procedure to select ,
Among the molding conditions generated by the molding condition generation means, a slide speed optimization procedure for selecting the optimal slide speed;
Using the molding condition generated by the molding condition generating unit as an analysis condition, a molding simulation analysis is performed by a molding simulation unit that executes a molding simulation using a stress-strain relationship. Based on the analysis result, the quality of the press molded product is determined. And a molding condition judgment procedure for judging whether or not a certain standard is reached,
The die cushion pressure optimization procedure, the molding condition determination procedure, the slide speed optimization procedure, and the molding condition determination procedure are repeated in this order until it is determined in the molding condition determination procedure that the quality of the press-molded product reaches a certain standard. Method for determining molding conditions of a press. In the molding condition determination method of the press according to claim 5,
In the molding condition determination procedure, whether or not the quality of the press-formed product reaches a certain standard based on the minimum principal strain and sheet thickness reduction rate, or the minimum principal strain and equivalent plastic strain, which is output as a molding simulation analysis result. A method for determining molding conditions for a press, characterized by: In the molding condition determination method of the press according to claim 5 or 6,
In the molding condition determination procedure, a molding simulation is executed using a stress-strain relationship, and the stress-strain relationship is determined in consideration of a strain rate. In the molding condition determination method of the press machine according to claim 7,
In the molding condition determination procedure, a molding simulation is executed using a friction coefficient, and the friction coefficient is determined in consideration of a sliding speed and a contact surface pressure between a material and a die of a press machine. Method for determining molding conditions for a press.

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